1. Field of the Invention
The present invention relates to a change rate prediction method, a storage medium, and a substrate processing system, and more particularly, to a method for predicting a change rate of a specification value of a film formed on a substrate, a storage medium in which is computer-readably stored a program for implementing the method, and a substrate processing system adapted to adjust intensities of electron beams irradiated onto the film based on measured values of the change rate of the specification value of the film.
2. Description of the Related Art
As the degree of integration of semiconductor devices has increased, wiring structures on substrates have become more minute. Reducing the parasitic capacitance caused by an insulating film between wires has thus become important. In recent years, various low-permittivity organic and inorganic materials for reducing the parasitic capacitance caused by an insulating film between wires have thus been developed. Of these materials, organic materials are used as low-k materials in interlayer insulating films, protective films and so on. Such a low-k film material is, for example, applied onto a surface of a substrate using a spin coater and then subjected to heat treatment using a baking oven, so as to form an SOD (spin-on dielectric) film as an interlayer insulating film. However, such an SOD film has a low mechanical strength due to being formed by applying a liquid material, and moreover due to the porosity being increased so as to secure low permittivity.
As a method of increasing the mechanical strength of an interlayer insulating film formed from a low-k film material, there is known a method in which a low-permittivity polymeric dielectric composition layer acting as an interlayer insulating film is exposed to electron beams so as to harden (modify, cure) the polymeric dielectric composition layer (see, for example, Published Japanese Translation of PCT Application No. 2000-511006).
A curing apparatus (substrate processing apparatus) for irradiating the interlayer insulating film with the electron beams so as to modify the interlayer insulating film has a plurality of electron beam tubes. The electron beam tubes are arranged uniformly in a horizontal plane directly above the substrate so that the interlayer insulating film on the substrate is irradiated uniformly with the electron beams from the electron beam tubes. Moreover, the curing apparatus has a stage having a heater built therein, the substrate which is mounted on the stage being heated by the heater. The low-k film material has the property of a thermosetting resin, and hence the interlayer insulating film can also be modified by the heating of the substrate.
Upon the interlayer insulating film being modified, the thickness of the interlayer insulating film decreases. Meanwhile, a plurality of semiconductor devices are formed on the substrate, and then cut out from respective places on the substrate. To eliminate individual differences between the semiconductor devices, it is necessary to make the shrinkage rate of the thickness of the interlayer insulating film on the substrate be uniform over the whole of the substrate.
However, the results of measuring the thickness of an interlayer insulating film modified by such a curing apparatus show that the shrinkage rate of the interlayer insulating film is not uniform over the substrate. For example, the shrinkage rate is high at a portion of the film directly below an electron beam tube, and is low at portions of the film in places away from the electron beam tube. The shrinkage rate of the interlayer insulating film is thus made uniform over the whole of the substrate by adjusting the intensities of the electron beams from the electron beam tubes in the curing apparatus. At this time, the intensities of the electron beams can be predicted to some extent by using commercially available simulation software that uses a Monte Carlo method or the like.
However, the electron beam intensities predicted using the commercially available simulation software are qualitatively accurate, but not quantitatively accurate. The shrinkage rate of the interlayer insulating film at each place on the substrate thus cannot be predicted quantitatively from the electron beam intensities predicted through the simulation, and hence it is difficult to make the shrinkage rate of the interlayer insulating film uniform over the whole of the substrate using such a simulation.
Instead of simulating the electron beam intensities, it is thus necessary to carry out experiments of modifying an interlayer insulating film on a substrate by irradiating the insulating film with the electron beams for several substrates while varying the electron beam intensities, and based on the experimental results, determine electron beam intensities that will enable the shrinkage rate of an interlayer insulating film on a substrate to be made uniform.